The present invention relates to a method of controlling channel assignment in a time division multiplexing network.
In known time division multiplexing networks such as a time division exchanger, a plurality of channels or time slots are previously established, and pulse trains are arranged having phase relationships that correspond to the channels, so that a large number of subscribers' lines may easily be connected to each other through a small number of time division channels. All the addresses of the addressors and the addressees are stored in a circulating memory for designating or assigning the channels to the addressors and addressees respectively.
Also, in establishing the channels, the encoding speed (sampling frequency) is specified to obtain a fixed demodulation quality (speech quality). That is, as shown in FIG. 1, n sampling pulse trains are arranged for n channels established, and a sampling pulse corresponding to a designated channel is supplied to a PAM modulation/demodulation circuit of each addressor and addressee, whereby PAM modulation/demodulation is performed respectively.
In a conventional control method, as above, a fixed quality of demodulation and good service having stabilized speech quality are provided, but on the contrary, the following defects are indicated:
(i) there is no countermeasure against traffic demands beyond the established number of channels;
(ii) the encoding efficiency per a time unit is low in the case where traffic demands are under the established number of channels; and
(iii) because a phase sampling pulse train corresponding to the established channels is provided separately, the whole structure of the control method becomes complex in addition to the inefficiency of the encoding speed.